| 摘要 |
A logarithmic amplifier gain stage for supplying, in response to an instantaneous input signal, an output signal representing a portion of a corresponding logarithmic value of the input signal. The gain stage includes a transistor amplifier having an input that receives the input signal and an intermediate output that supplies an intermediate output signal. A full-wave detector having an input coupled to the intermediate output of the transistor amplifier receives the intermediate output signal and supplies the output signal wherein the detector includes a rectifier comprising transistors having different effective emitter areas. The different emitter areas can be formed by physical differences in emitter area of the full-wave rectifier transistors. In another embodiment of the invention, the different emitter areas can be synthesized by controlling a voltage between a base and an emitter of at least one transistor in the full-wave rectifier. The full-wave detector performs the demodulating function and also drives the input of a succeeding gain stage.
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